Identification media such as plastic credit cards and debit cards have become widely employed in commerce, particularly in retail and financial systems, for the purpose of positively and accurately identifying to the system the legitimacy of the card to enable the holder of the card to consummate a desired transaction. In many instances, a magnetic stripe has been incorporated into the card to permit various categories of customer and account information to be read from and optionally written on the card by suitable electronic equipment associated with the system.
The ease of reading from and writing on the magnetic stripe has become a source of fraud in debit and credit card usage. Without great effort or extensive knowledge of the system, a criminal can counterfeit or duplicate a card, and the data stored on the magnetic stripe of the card can be altered, to allow fraudulent access to the system. Various ways of producing counterfeit cards or altering magnetic stripe information on legitimate cards have been well documented in the literature.
In order to thwart the possibility of such criminal actions which could result in substantial financial loss to the proprietors of the systems with which the cards are used, the concept of a "secure" card has been introduced. Secure card techniques may rely upon the incorporation of permanent physical uniqueness data in the structure of a card, with said data not being subject to alteration, so that one card may be distinguished from another by sensing of this physical data. In order to avoid excessive complications in card manufacture and distribution, it is highly desirable that this uniqueness data be independent of customer-related information, such as an account number. Incorporating the account number into the uniqueness data, for example, would seriously disrupt present card manufacturing and distribution practices. With the uniqueness information independent of the customer-related information, it then becomes important from the requirement of positive and accurate card validity determination to provide a verification means which encompasses both the uniqueness information and the customer-related information.